1. Field of the Invention
The present invention relates to internal combustion engines, and, more particularly, to an exhaust system for an internal combustion engine which includes an ejector device, for the creation of a negative pressure which draws dust-laden air from the air intake filter of the internal combustion engine.
2. Description of the Prior Art
Ejector devices of the type referred to above are known from the prior art. In general, they take advantage of the flow speed of the exhaust gas, using a venturi-type flow pipe arrangement in the exhaust system to create a negative pressure which, when connected to the air intake filter of the internal combustion engine, draws dust-laden air from the latter into the exhaust system.
Under certain operating conditions, it may happen that, instead of the desired negative pressure, the ejector device in the exhaust system briefly produces a positive pressure, or a negative pressure so weak that it is overcome by the negative pressure inside the air intake filter. When this happens, hot exhaust gas will flow to the air filter, carrying with it exhaust impurities and particulate matter.
In order to prevent such a reverse flow to the air intake filter, it has already been suggested that the filter should be equipped with a check valve. Such an arrangement has the advantage of determining a single, unchangeable mounting arrangement of the check valve, so that the pivot axis of the valve element is always oriented in the same way, horizontally, for example. This feature, by preventing other orientations of the pivot axis, under which the valve operation is a different one, increases the operational reliability of the system. A disadvantage of this prior art arrangement is that it requires a modified air filter assembly, specially adapted for use with an ejector device. This reflects itself in higher costs of production and spare parts distribution, because separate air filter assemblies must be stocked for combustion engines which have an ejector device and for those not equipped with such a device.
One way of overcoming the aforementioned problem is suggested in U.S. Pat. No. 3,419,892. This prior art solution suggests the arrangement of a check valve in the form of a separate subassembly enclosed within a housing which is mounted in the hose connection between the air intake filter and the ejector device, in the vicinity of the filter housing. The need for a separate housing and for suitable connectors on both sides of the housing means that this is likewise a costly solution.